With the environmental consciousness rising, the people pay much attention on contamination of semiconductor manufacturing process. Some manufacturers introduce lead-free solder bump in the manufacturing process for contamination reduction. However, the lead-free solder bump behaves brittleness and likely leads a crack phenomenon. Besides, mismatch of the thermal expansion coefficient between a chip and a substrate enables to generate a stress, and the reliability of lead-free package system is directly impacted by mentioned stress. In addition, present underfill may not provide the lead-free solder bump with sufficient protection therefore resulting lower production reliability.